This invention relates generally to fluidized bed furnaces and more particularly, it relates to a fluidized bed furnace having a vertical retort.
In recent years, there has been an increased demand for furnaces in which a charge or work may be heated through high temperatures. There are a number of problems associated with the heat-treating of a material to high temperatures which have not heretofore been adequately solved by the prior art furnaces. One of the problems that existed in the prior art is the failure to create a well sealed enclosure for the work or charge to be heated so as to prevent loss of the fluidizable media. Since it is well known that high temperatures and pressures are required in furnace applications, there has been encountered another problem of fabricating a retort structure which will allow for thermal growth. In other words, there is a need to develop a retort structure which prevents structural cracks in the sidewalls as the result of internal pressures produced by the load in the retort or the influence of gases or as a result of the expansion or contraction of the materials forming the retort when they are heated and cooled through a wide range of temperatures. Still another problem experienced in the prior art furnaces is that the retorts have a short service life due to the fact that they cannot withstand prolonged periods of operation without the development of cracks or fractures in the body of the retort.
Therefore, it would be desirable to provide a fluidized bed furnace having a vertical retort which has an effective seal and allows for thermal growth so as to increase its service life. The retort of the present invention is supported and sealed at its top at a fixed position which permits downward growth only during thermal expansion. Further, a lower support structure is provided at the bottom or lower end of the present retort so as to take up a substantial amount of the load when thermal growth of the retort occurs.